+ mm-damon-core-set-ctx-call_controls_obsolete-in-damon_new_ctx.patch added to mm-new branch

+ mm-damon-core-set-ctx-call_controls_obsolete-in-damon_new_ctx.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/core: set ctx->call_controls_obsolete in damon_new_ctx()
has been added to the -mm mm-new branch.  Its filename is
     mm-damon-core-set-ctx-call_controls_obsolete-in-damon_new_ctx.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-set-ctx-call_controls_obsolete-in-damon_new_ctx.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: SJ Park <sj@kernel.org>
Subject: mm/damon/core: set ctx->call_controls_obsolete in damon_new_ctx()
Date: Wed, 2 Sep 2026 18:03:31 -0700

damon_ctx->call_controls_obsolete is used to disallow damon_call()
requests when the request cannot be served.  The field is unset and set
when the context execution is started and terminated, respectively.  The
intention is to allow damon_call() requests only while the context is
actively being executed.

damon_ctx constructor, damon_new_ctx() unsets the field, though.  As a
result, passing the damon_ctx parameter that never successfully
damon_start()-ed to damon_call() can indefinitely hang.  The callers
should ensure to avoid the case.  Such parameter validation is not always
simple.  Actually such bugs in DAMON_RECLAIM and DAMON_LRU_SORT have been
found and fixed [1].

Set the field in damon_new_ctx(), so that DAMON API callers can pass the
context parameter to damon_call() without the additional check.

Link: https://lore.kernel.org/20260903010334.93622-3-sj@kernel.org
Link: https://lore.kernel.org/20260803134646.16640-1-sj@kernel.org [1]
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/core.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-set-ctx-call_controls_obsolete-in-damon_new_ctx
+++ a/mm/damon/core.c
@@ -933,6 +933,7 @@ struct damon_ctx *damon_new_ctx(void)
 	INIT_LIST_HEAD(&ctx->adaptive_targets);
 	INIT_LIST_HEAD(&ctx->schemes);
 
+	ctx->call_controls_obsolete = true;
 	prandom_seed_state(&ctx->rnd_state, get_random_u64());
 
 	return ctx;
@@ -2206,10 +2207,6 @@ int damon_kdamond_pid(struct damon_ctx *
  * synchronization.  The return value of the function will be saved in
  * &damon_call_control->return_code.
  *
- * Note that this function should be called only after damon_start() with the
- * @ctx has succeeded.  Otherwise, this function could fall into an indefinite
- * wait.
- *
  * When this function is failed, the @ctx is guaranteed to be stopped.
  *
  * Return: 0 on success, negative error code otherwise.
_

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-core-skip-applying-scheme-if-region-split-for-quota-fails.patch
mm-damon-paddr-respect-folio-end-for-damos_stat.patch
mm-damon-paddr-respect-folio-end-for-damos-actions-except-stat.patch
mm-damon-vaddr-respect-folio-end-for-damos_stat.patch
mm-damon-vaddr-respect-folio-end-for-damos_migrate_hotcold.patch
mm-damon-core-handle-extreme-memory-state-in-damon_get_node_mem_bp.patch
mm-damon-core-handle-extreme-memory-state-in-get_node_memcg_used_bp.patch
mm-damon-core-handle-extreme-memory-state-in-get_in_active_mem_bp.patch
mm-damon-core-introduce-damon_filter_type_pgidle_unset.patch
mm-damon-paddr-support-pgidle_unset-probe-filter-type.patch
mm-damon-sysfs-support-pgidle_unset-probe-filter-type.patch
docs-mm-damon-design-document-pgidle_unset-probe-filter-type.patch
mm-damon-core-introduce-damon_prep-struct.patch
mm-damon-core-commit-preps.patch
mm-damon-core-introduce-damon_operations-prep_probes.patch
mm-damon-paddr-support-damon_prep.patch
mm-damon-sysfs-implement-preps-directory.patch
mm-damon-sysfs-implement-preps-nr_preps-file.patch
mm-damon-sysfs-create-directories-for-nr_preps-writes.patch
mm-damon-sysfs-implement-prep_action-file.patch
mm-damon-sysfs-pass-preps-to-damon-core.patch
selftests-damon-sysfssh-test-probe-prep-sysfs-files.patch
docs-mm-damon-design-document-probe-preps.patch
docs-admin-guide-mm-damon-usage-document-probe-preps-sysfs-files.patch
docs-abi-damon-document-probe-prep-sysfs-files.patch
mm-damon-tests-core-kunit-test-committing-psi-goal-to-psi-goal.patch
mm-damon-core-handle-uninitialized-damos_quota_goal-last_psi_total.patch
mm-damon-core-copy-nid-for-eligible_mem_bp-damos-quota-goal-commit.patch
mm-damon-sysfs-set-next-refresh-jiffies-per-sysfs-context.patch
mm-damon-tests-core-kunit-test-damon_commit_filter.patch
mm-damon-tests-core-kunit-add-damon_commit_probes-test.patch
selftests-damon-_damon_sysfs-implement-damonprobes.patch
selftests-damon-drgn_dump_damon_status-dump-probes.patch
selftests-damon-sysfspy-extend-commit-assertion-function-for-probes.patch
selftests-damon-sysfspy-test-damon-probes.patch
mm-damon-core-use-damon_nr_samples_per_aggr-for-max-merge-threshold.patch
mm-damon-core-remove-debug-messages.patch
mm-damon-core-remove-debug-messages-fix.patch
mm-damon-vaddr-remove-a-debug-message.patch
mm-damon-core-validate-number-of-probes-in-valid_probe_params.patch
mm-damon-sysfs-remove-probes-number-validation.patch
mm-damon-tests-core-kunit-extend-set_regions-test-for-error-case.patch
mm-damon-tests-core-kunit-test-=0-size-damon_set_regions-inputs.patch
mm-damon-tests-core-kunit-test-overlapping-ranges-for-set_regions.patch
mm-damon-tests-core-kunit-test-damon_nr_samples_per_aggr.patch
selftests-damon-sysfssh-test-hugepage_mem_bp-quota-goal.patch
docs-mm-damon-maintainer-profile-update-ai-review-for-sashiko-replies.patch
docs-abi-damon-recommend-subsystem-doc-instead-of-admin-guide.patch
mm-damon-core-error-damos_commit_quota_goal-for-zero-target_value.patch
revert-mm-damon-lru_sort-error-out-for-10000-active_mem_bp.patch
revert-samples-damon-mtier-error-out-for-zero-quota-goal-target-values.patch
mm-damon-core-handle-null-ctx-parameter-in-damon_call.patch
mm-damon-core-set-ctx-call_controls_obsolete-in-damon_new_ctx.patch
mm-damon-reclaim-remove-unnecessary-damon_call-param-validation.patch
mm-damon-lru_sort-remove-unnecessary-damon_call-param-validation.patch